Figs. 1-2. Adult male characters of Isoperla acula, Deadman Cr., El Dorado Co., CA and I. adunca, Campbell Cr. & Trib., Butte Co., CA, 32-50x. Fig. 1a. I. acula aedeagus, lateral; fine spinule patch (arrow). Fig. 1b. Aedeagus, ventral; fine spinule patches (arrow & inset-posterior view). Fig. 1c. Paraprocts, (black arrow); abdominal spinules (white arrow). Fig. 1d. Vesicle; brush setae (inset). Fig. 2a. I. adunca aedeagus, lateral; sclerotized process (arrow & inset-lateral view). Lobes A: posterobasal, B: posteromedian, C: anterior, D: dorsomedian pair. Fig. 2b. Aedeagus, ventral; sclerotized process (arrow & inset-posterior view). Fig. 2c. Paraprocts (arrow). Fig. 2d. Vesicle.

Published as part of Sandberg, John B. & Kondratieff, Boris C., 2013, The Isoperla Of California (Plecoptera: Perlodidae); Updated Male Descriptions And Adult Keys For 18 Western Nearctic Species, pp. 34-64 in Illiesia 9 (5) on page 40, DOI: 10.5281/zenodo.4760870